玉米籽粒收获机清选装置多四棱锥筛设计与试验

Design and Experiment of Multi-tetragonal Conical Sieve for Maize Grain Harvester Cleaning Device

摘要:

为提高玉米籽粒收获机清选装置在大喂入量条件下的性能，设计了一种多四棱锥筛，通过非平面结构使筛上玉米籽粒滞留并快速透筛。依据理论分析确定了多四棱锥筛的关键结构参数，采用CFD-DEM耦合仿真对多四棱锥清选装置内气固两相运动进行了数值模拟。结果表明：在玉米混合物喂入量为7kg/s时，多四棱锥筛筛前出现了一条高速气流带，有利于混合物的分离，筛体中部气流速度较低，有利于配合多四棱锥筛结构使玉米籽粒滞留，在多四棱锥筛的运动下，筛上玉米籽粒完成“撞筛—滞留—跃起—撞筛—透筛”，筛上混合物未出现堆积现象，筛上玉米籽粒完成快速透筛。以多四棱锥筛单元体高度、清选装置入口气流速度、振动筛振动幅度为试验因素，以玉米籽粒的含杂率、损失率、筛分速率为清选装置性能的评价指标，进行了二次正交旋转组合试验，建立了各因素与指标间的数学模型，获得了各参数的最优组合为：多四棱锥筛单元体高度11.26mm、清选装置入口气流速度9.6m/s、振动筛振动幅度15.13mm。通过高速摄像台架试验验证了筛上玉米籽粒的运动规律；在玉米混合物喂入量为7kg/s时，多四棱锥筛清选装置籽粒的含杂率为1.68%，损失率为1.33%，筛分速率为3.66kg/s，均满足国家标准要求，多四棱锥筛清选装置可以完成喂入量7kg/s下玉米籽粒清选作业。

Abstract:

Aiming to improve the cleaning performance of maize grain harvester cleaning device under the condition of large feeding mass, a multi-tetragonal conical sieve was designed to make the maize grains on the sieve retained and quickly penetrate the sieve through the non-planar structure. The key structural parameters of the multi-tetragonal conical sieve were determined by theoretical analysis. CFD-DEM method was used for numerical simulating the motion of gas-solid two-phase in multi-tetragonal conical sieve cleaning device. A high speed airflow belt could be formed in front of the multi-tetragonal conical sieve, which was beneficial to make maize mixtures separated. The air velocity in the middle of the sieve body was low, which was conducive to the retention of maize grain with the structure of multi-tetragonal conical sieve. The maize grain on the sieve completed the process of ‘impact sieve-retention-leaping-impact sieve-through the sieve’ under the movement of multi-tetragonal conical sieve. No build-up of the maize mixture on the sieve. The maize grain on the sieve completed rapid penetration of the sieve. The height of multi-tetragonal conical sieve unit, the airflow velocity at the inlet of the cleaning device and the vibrating amplitude of the vibrating sieve were selected as the test factors. The impurity rate, loss rate and screening efficiency of maize grain were selected as test indexes. The quadratic orthogonal rotation combination test was carried out. The mathematical models between factors and indicators were established. The best combination of parameters was obtained as follows, the height of the multi-tetragonal conical sieve unit was 11.26mm, the airflow velocity of the cleaning device was 9.6m/s, the vibration amplitude of the vibrating screen was 15.13mm. The motion law of maize grains on the sieve was verified through the bench validation test. At the maize mixture feeding mass of 7kg/s, the impurity rate of maize grain after screening by the multi-tetragonal conical sieve cleaning device was 1.68%, the loss rate of maize grain was 1.33%, and the screening efficiency of maize grain was 3.66kg/s. The multi-tetragonal conical sieve cleaning device could meet the requirements of cleaning maize mixtures with large feed mass. The research result had a certain reference value for improving the working performance of maize grain combine harvester.